Get file/directory size using Java 7 new IO

Question

How can I get the size of a file or directory using the new NIO in java 7?

What's wrong with the old way? Unless there is support for recursive directory size now. Is there? — Thilo, Aug 31 '11 at 10:23
i think its because the check if a java.io.File is a directory or not is very slow. — clamp, Aug 31 '11 at 10:37
for example here: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6483858 and here: http://stackoverflow.com/questions/354703/is-there-a-workaround-for-javas-poor-performance-on-walking-huge-directories — clamp, Aug 31 '11 at 10:53
@clamp: at least the second item can *indeed* be solved by using `Path`: since it returns an `Iterator`, it doesn't need to have resolved all members of the directory at the time the `iterator()` call returns and thus can "stream" the directory content, which more closely aligns with the native APIs on most OSes. — Joachim Sauer, Aug 31 '11 at 11:24

score 68 · Accepted Answer · answered Aug 31 '11 at 10:24

68

Use Files.size(Path) to get the size of a file.

For the size of a directory (meaning the size of all files contained in it), you still need to recurse manually, as far as I know.

answered Aug 31 '11 at 10:24

Joachim Sauer

302,674
57
556
614

I think above method is not present in Java7 I/O, Please check once – developer Aug 31 '11 at 10:28
2

@Damodar: my answer contains a link to the JavaDoc. Why do you think that it's not present? – Joachim Sauer Aug 31 '11 at 10:28
2

He linked to Oracle's official API docs. The method is there. – Thilo Aug 31 '11 at 10:29
thanks, then my next question would be, how would i recurse into a path's childpaths? – clamp Aug 31 '11 at 10:37
2

@clamp: a `Path` *is* an `Iterable`, so you can just do `for (Path child : parent) { /* do stuff */ }`. – Joachim Sauer Aug 31 '11 at 10:38

score 6 · Answer 2 · answered Nov 08 '13 at 22:02

Here is a ready to run example that will also skip-and-log directories it can't enter. It uses java.util.concurrent.atomic.AtomicLong to accumulate state.

public static void main(String[] args) throws IOException {
    Path path = Paths.get("c:/");
    long size = getSize(path);
    System.out.println("size=" + size);
}

static long getSize(Path startPath) throws IOException {
    final AtomicLong size = new AtomicLong(0);

    Files.walkFileTree(startPath, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult visitFile(Path file,
                BasicFileAttributes attrs) throws IOException {
            size.addAndGet(attrs.size());
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult visitFileFailed(Path file, IOException exc)
                throws IOException {
            // Skip folders that can't be traversed
            System.out.println("skipped: " + file + "e=" + exc);
            return FileVisitResult.CONTINUE;
        }
    });

    return size.get();
}

Wondering why the `AtomicLong` is necessary? Why not just a `long` ? Is there something parallel about [walkFileTree](http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#walkFileTree%28java.nio.file.Path,%20java.util.Set,%20int,%20java.nio.file.FileVisitor%29) ? — peterh, Jan 21 '14 at 09:25
tbh, i just rewrote the other answer without using 3pp (MutableLong). But I think the variable has to be "final" to be accessed from the inner anonymous class. Which AtomicLong allows. — Aksel Willgert, Jan 21 '14 at 11:42
The method `postVisitDirectory`may be also overriden. It's not required to mark the `size` reference as final here because it isn't changed in the inner anonymous class. Only its content (value) is changed. A long array (with one single element) can be used in place of AtomicLong. — Stephan, Sep 16 '17 at 08:36

Ivan Senic · Answer 3 · 2012-11-26T11:29:39.833

MutableLong size = new MutableLong();
Files.walkFileTree(directoryPath, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                size.add(attrs.size());
            }
}

This would calculate the size of all files in a directory. However, note that all files in the directory need to be regular files, as API specifies size method of BasicFileAttributes:

"The size of files that are not regular files is implementation specific and therefore unspecified."

If you stumble to unregulated file, you ll have either to not include it size, or return some unknown size. You can check if file is regular with

BasicFileAttributes.isRegularFile()

Nice answer, and for anyone wondering the Mutable* classes for primitives are part of apache.commons.lang — Nicholi, Oct 01 '12 at 22:16

Get file/directory size using Java 7 new IO

3 Answers3

Linked